The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Generally, ISG (Idle Stop and Go) is an engine idle stop control which means idle stop and go and contributes to improvement in fuel efficiency of a vehicle by determining whether an engine is idle using information of a vehicle speed, an engine revolution per minute (RPM), cooling water temperature, etc., and then repeatedly stopping and restarting the engine. Accordingly, ISG technology has been applied to gasoline or diesel vehicles as well as hybrid vehicles to improve fuel efficiency.
Among the vehicles in which the ISG is equipped as described above, a diesel ISG vehicle links a rail pressure control mode of a common rail with ISG logic to perform a rail pressure control in an order of an outlet control (hereinafter, PCV control)→inlet/outlet control (hereinafter, CPC control)→inlet control (hereinafter, MeUn control) at the time of engine restarting by the idle go.
Here, the common rail means a component of a fuel injection apparatus in which high pressure fuel pumped by a high pressure pump stays before being injected into a combustion chamber to meet operation conditions. The PCV means a pressure control valve included in the common rail to control a fuel flow rate and the PCV control is a control mode to which only a rail pressure control is applied and operates the high pressure pump which increases a pressure of fuel delivered from a low pressure pump pumping fuel within a fuel tank to pump the fuel to the common rail. The MeUn means a metering unit valve included in the fuel pump to open and close a flow of fuel and the MeUn control is a control mode to which only a fuel pressure control is applied. The CPC means a coupled pressure control and the CPC control is a control mode to which both of a rail pressure control and a fuel pressure control are applied and operates the high pressure pump which increases a pressure of the fuel delivered from the low pressure pump pumping the fuel within the fuel tank to pump the fuel to the common rail.
However, among the rail pressure control modes performed at the time of the engine restarting by the ISG, the PCV control and the CPC control is advantageous only at the time of initial cold start required to increase a temperature of fuel and form the rail pressure, but increases a driving torque of the high pressure pump which leads to a loss of accessories such as a pump and a compressor. Therefore, the operation based on the PCV/CPC control mode at the time of frequently restarting the engine by the ISG increases the driving torque of the high pressure pump, which negatively impacts fuel efficiency.